1. Field of the Invention
The invention relates to a ball bearing that includes an outer ring, an inner ring, balls, and lubricant supply members.
2. Description of the Related Art
Japanese Patent Application Publication No. 2002-357227 (JP 2002-357227 A) describes a conventional ball bearing. The ball bearing includes an outer ring, an inner ring, a plurality of balls, and two shield plates. The balls are disposed between a raceway groove of the outer ring and a raceway groove of the inner ring. One of the shield plates seals one axial end of a ball arrangement chamber that is defined by the inner periphery of the outer ring and the outer periphery of the inner ring. The other one of the shield plates seals the other axial end of the ball arrangement chamber. Grease is sealed in the ball arrangement chamber.
A radially outer end of each shield plate is fixed to the inner periphery of the outer ring, whereas a radially inner end of each shield plate is located with a small clearance left between the radially inner end and the inner ring. In the ball bearing, a labyrinth seal is formed by the radially inner end of each shield plate and the outer periphery of the inner ring as described above to prevent the grease from leaking outside from the ball arrangement chamber. The labyrinth seal also prevents foreign matter from entering the ball arrangement chamber from the outside.
There has been a demand that the torque generated in the conventional ball bearing should be reduced. However, if the amount of grease sealed in the ball arrangement chamber is reduced to reduce the stirring resistance in an attempt to reduce the torque, seizure of the raceway grooves or the like may occur.